The First Symposium on Subtypes of Muscarinic Receptors, held in 1983, was the first to probe a field that had been ignored for years by all but a few investigators. As a result of research directed at a practical problem of therapeutics, the concept of subtypes of the muscarinic receptor became a reality and a whole field of research was energized into rapid growth. In the short span of time since the first symposium three subtypes have been clearly defined on the basis Of new and selective antagonists and the sequences, distribution, and coupling mechanisms of 5 muscarinic receptors largely disclosed. The Sixth symposium will continue the precedents set by the previous symposia by increasing our basic knowledge of muscarinic receptors and disclosing new agonists and antagonists of potential or demonstrated therapeutic value. The major goals of the Sixth Symposium are to provide a forum for interaction between individuals who are actively studying muscarinic receptor function and investigators who are actively pursuing the identity and structure of receptor subtypes with technologies evolved from molecular cloning. The broad areas to be covered include: 1) the development and medicinal chemistry of selective agonists and antagonists; 2) the clinical relevance of new, selective agents, particularly with respect to pulmonary function and Alzheimer's Disease; 3) phase 2 and phase 3 studies of cholinergic agents in senile dementia; 4) molecular pharmacology and physiology of muscarinic receptors emphasizing function relationships based on mutagenesis and interactions with other systems, and 5) new insights into coupling mechanisms. This symposium provides a unique opportunity for interaction between biochemists, physiologists, pharmacologists and neuroscientists who are the leaders in the multidisciplinary approach being taken in the field and young investigators who will present their work in the poster sessions. This symposium will also be the occasion for the first Otto Loewi New Investigator Awards and Lectures sponsored and supported by the Symposium.